The effect of gas ion bombardment on the secondary electron yield of TiN, TiCN and TiZrV coatings for suppressing collective electron effects in storage rings

Abstract

In many accelerator storage rings running positively charged beams, multipactoring due to secondary electron emission (SEE) in the beam pipe will give rise to an electron cloud which can cause beam blow-up or loss of the circulating beam. A preventative measure that suppresses electron cloud formation is to ensure that the vacuum wall has a low secondary emission yield (SEY). The SEY of thin films of TiN, sputter deposited Non-Evaporable Getters and a novel TiCN alloy were measured under a variety of conditions, including the effect of re-contamination from residual gas.

Measurements of electron cloud growth and mitigation in dipole, quadrupole, and wiggler magnets

“…• TiN coating [20][21][22][23], which reduces the secondary emission yield (SEY) of the coated chamber.…”

Experimental observations of in situ secondary electron yield reduction in the PEP-II particle accelerator beam line

“…Note that in the apparatus, the SEY is measured with the use of an electron beam incoming at a 23° angle with respect to the sample surface normal. The SEY of technical surfaces material for accelerator vacuum chamber has been measured in the past at CERN [11,12] at KEK [13,14,15] SLAC [9,16,17] and at other laboratories [18]. 4…”

“…The impact of particles on a metallic surface reduces the surface SEY to low values [9][10][11][12][13][14][15][16][17]. This effect is known as conditioning.…”

“…In those energy ranges, the ions are very effective at sputtering the surface [17,22]. The cumulative charge of ions necessary to reduce the SEY max of TiN or NEG films, to a value obtained after electron conditioning is a factor 2000 lower [17]. The ion dose is calculated according to the PEP II beam parameters, …”

Deposition and characterization of TiZrV-Pd thin films by dc magnetron sputtering

“…Titanium-Zirconium-Vanadium (TiZrV) as one of nonevaporable getters (NEGs) [1][2][3][4] has been extensively studied during the past two decades for low secondary electron yield [5][6][7] and their sorption properties toward many gases such as hydrogen, oxygen, nitrogen, carbon monoxide and dioxide. The sorption of these gases except H2 is not reversible and it causes a progressive contamination for TiZrV film [1,8,9].…”